I don't know about done, but at least starting stuff will be when the Tactical Combat mod is done. We need this for the separate maps. That's not to say terrain, units and builds cannot be worked on ahead of time. The tech tree for the most part is already done. However as we add more features we may need to add, replace or remove techs from the tree to better fit. This is the method we used for the prehistoric era.
I also think that the nomad camp code would be very useful for space colonization so we may need to make that before we have a playable space game.
Do we really need to wait for the tactical combat mod to be done, or could we have Koshling and AIAndy get to work on it whenever? That would mean more work for them, but I have no idea how fast the TC mod is developing or when a release will be available.